Metering valves are well known and they generally comprise a valve body in which a valve member slides between a rest position and a dispensing position. The valve includes a metering chamber that defines a quantity or “dose” of fluid that is to be dispensed on each actuation of the valve. The metering chamber is generally connected to the dispenser orifice of the valve member while said valve member is in its dispensing position, and it is filled with the fluid contained in the reservoir while the valve member is returning from its dispensing position to its rest position. Generally, the metering chamber is formed by a cylindrical tubular element associated with two horizontal annular walls that define the axial ends of said metering chamber, each including a central through hole for the valve member. To ensure that the valve member is displaced in leaktight manner relative to the metering chamber, the two through holes are generally associated with sealing gaskets. A well known problem with metering valves relates to the reproducibility or repetitivity of the metered dose,. i.e. a metered dose that is accurate and identical on each actuation. Conventional metering chambers present a drawback in that they define a corner or an angle at the junction between the cylindrical tube and each of the horizontal annular wall elements. The fluid contained in the metering chamber, generally a fluid containing a propellant gas, is capable of forming a meniscus at the angles or corners of the metering chamber. This causes propellant and active fluid to be retained at the meniscuses, and therefore spoils the accuracy of the metered dose. In addition, that type of meniscus causes fluid to adhere to the walls of the chamber, which also spoils the uniformity of the metered dose. In particular, when a metering valve is actuated, the user presses axially on the valve member, and holds it in its dispensing position for a limited period of time. If the metering chamber presents a meniscus during actuation, then actuating the valve member relatively rapidly would not enable the entire dose contained in the metering chamber to be dispensed. In this event, in order to improve metering accuracy, it is necessary to hold the valve member driven in, in its dispensing position, for a relatively long period of time, typically several seconds, and that constitutes a significant drawback.